*
     * @return {@code true} if the dependency is optional, or {@code false} if mandatory
     * @see DependencyCoordinates#getOptional()
     */
    boolean isOptional();

    /**
     * {@return coordinates with the same identifiers as this dependency}
     */
    @Nonnull
    @Override
    DependencyCoordinates toCoordinates();

    isOptional: Boolean = false,
    optionalValue: Any? = null,
  ): DerAdapter<Any?> {
    return object : DerAdapter<Any?> {
      override fun matches(header: DerHeader): Boolean = true

      override fun toDer(
        writer: DerWriter,
        value: Any?,
      ) {
        when {
          isOptional && value == optionalValue -> {
            // Write nothing.

            Artifact artifact = (Artifact) iter.next();
            System.out.println("Artifact: " + artifact.getDependencyConflictId() + " " + artifact.getVersion()
                    + " Optional=" + (artifact.isOptional() ? "true" : "false"));
            assertTrue(
                    artifact.getVersion().equals("1.0"), "Incorrect version for " + artifact.getDependencyConflictId());
        }
    }

            Artifact artifact = (Artifact) aSet;
            System.out.println("Artifact: " + artifact.getDependencyConflictId() + " " + artifact.getVersion()
                    + " Optional=" + (artifact.isOptional() ? "true" : "false"));
            assertTrue(
                    artifact.getVersion().equals("1.0"), "Incorrect version for " + artifact.getDependencyConflictId());
        }
    }

                return session.requireDependencyScope(scope);
            }

            @Override
            public Boolean getOptional() {
                return dependency.isOptional();
            }

            @Nonnull
            @Override
            public Collection<Exclusion> getExclusions() {
                return new MappedCollection<>(dependency.getExclusions(), this::toExclusion);

    }

    @Override
    public void setAvailableVersions(List<ArtifactVersion> availableVersions) {
        this.availableVersions = availableVersions;
    }

    @Override
    public boolean isOptional() {
        return optional;
    }

    @Override
    public ArtifactVersion getSelectedVersion() throws OverConstrainedVersionException {
        return versionRange.getSelectedVersion(this);
    }

                .append(":")
                .append(dependency.getVersion())
                .append("@")
                .append(dependency.getScope() == null ? "compile" : dependency.getScope());
        if (dependency.isOptional()) {
            stringBuilder.append("[optional]");
        }
        if (!dependency.getExclusions().isEmpty()) {
            stringBuilder.append("[").append(dependency.getExclusions().size()).append(" exclusions]");

        }

        return new Dependency(
                artifact,
                dependency.getScope(),
                dependency.getOptional() != null ? dependency.isOptional() : null,
                exclusions);
    }

    private Exclusion convert(org.apache.maven.model.Exclusion exclusion) {
        return new Exclusion(exclusion.getGroupId(), exclusion.getArtifactId(), "*", "*");

                            // we don't add it or its children, just allow the update of the version and artifactScope
                            if (node.isChildOfRootNode() || !artifact.isOptional()) {
                                artifact.setDependencyTrail(node.getDependencyTrail());

                                set.add(node);

                                // This is required right now.

                dependency.getArtifactId(),
                versionRange,
                dependency.getType(),
                dependency.getClassifier(),
                effectiveScope,
                dependency.isOptional());

        if (inheritedFilter != null && !inheritedFilter.include(dependencyArtifact)) {
            return null;
        }

        if (Artifact.SCOPE_SYSTEM.equals(effectiveScope)) {